Muscle Contraction Signaling Pathway
28 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a key difference between smooth muscle and skeletal muscle contractions?

  • Skeletal muscles respond to a variety of stimuli, while smooth muscles only respond to excitatory stimuli
  • Smooth muscles contract faster than skeletal muscles
  • Skeletal muscles create more tension over a long period of time (correct)
  • Smooth muscles lack striations, while skeletal muscles have z lines

    • Where is actin bound in smooth muscles and what does it anchor to?

  • Actin is bound to dense bodies and anchors to extracellular fluid (correct)
  • Actin is bound to z lines and anchors to the sarcoplasmic reticulum
  • Actin is bound to troponin and anchors to the ECF
  • Actin is bound to myosin and anchors to the cytoplasm

    • How are neurons connected to smooth muscles compared to skeletal muscles?

  • Neurons in smooth muscles form neuromuscular junctions with muscle fibers
  • Neurons in smooth muscles are directly connected to each muscle fiber
  • Neurons in smooth muscles are not directly connected like in skeletal muscles (correct)
  • Neurons in skeletal muscles do not influence muscle contractions

    • Why do autonomic nerves connect to smooth muscles instead of somatic nerves?

    <p>Autonomic nerves can control involuntary functions like smooth muscle contractions</p> Signup and view all the answers

    What is a distinguishing feature of autonomic neurons at the junction of smooth muscles?

    <p>They can modulate the strength and speed of muscle contractions in smooth muscles</p> Signup and view all the answers

    What is the neurotransmitter released by autonomic nerves?

    <p>Norepinephrine</p> Signup and view all the answers

    Which system is associated with norepinephrine?

    <p>Sympathetic</p> Signup and view all the answers

    What type of muscle undergoes mitosis and hyperplasia?

    <p>Smooth muscle</p> Signup and view all the answers

    What is the purpose of the circular arrangement of smooth muscle in the viscera?

    <p>Controls lumen size</p> Signup and view all the answers

    Which type of smooth muscle can contract as a unit due to gap junctions?

    <p>Single unit smooth muscles</p> Signup and view all the answers

    How can calcium concentration decrease in a smooth muscle cell?

    <p>Via a second messenger IP3 pathway</p> Signup and view all the answers

    Which of the following is a direct effect of parasympathetic innervation?

    <p>Stimulating saliva production</p> Signup and view all the answers

    Where is the primary concentration of sympathetic innervation?

    <p>Sympathetic trunk</p> Signup and view all the answers

    Which type of cholinergic receptor is classified as second messengers?

    <p>Muscarinic receptors</p> Signup and view all the answers

    What is the primary action of alpha 2 adrenergic receptors?

    <p>Inhibited release of catecholamines</p> Signup and view all the answers

    What is the primary neurotransmitter that alpha 1 adrenergic receptors respond to?

    <p>Norepinephrine</p> Signup and view all the answers

    Which drugs are commonly used to block beta 1 adrenergic receptors?

    <p>'Metoprolol'</p> Signup and view all the answers

    What is the triad of symptoms associated with Horner’s syndrome?

    <p>'Ptosis, miosis, anhidrosis'</p> Signup and view all the answers

    How is acetylcholine removed from a synaptic cleft?

    <p>Hydrolyzed by acetylcholinesterase</p> Signup and view all the answers

    What is the primary role of beta 1 adrenergic receptors?

    <p>Increasing heart rate and contractility</p> Signup and view all the answers

    What is the role of Ca-Calmoudilin in smooth muscle contraction?

    <p>Forms a complex with myosin light chain kinase</p> Signup and view all the answers

    In smooth muscle contraction, what is the significance of myosin ATPase?

    <p>Cleaves ATP into ADP and Pi</p> Signup and view all the answers

    What factor contributes to maintaining a long period of tension in smooth muscle contraction?

    <p>Latch bridge mechanism</p> Signup and view all the answers

    Which neurotransmitter is released from the adrenal glands during adrenal innervation?

    <p>Epinephrine (EP)</p> Signup and view all the answers

    What is the main function of postganglionic fibers in the autonomic nervous system?

    <p>Conduction of nerve impulses away from ganglia</p> Signup and view all the answers

    In sympathetic innervation, where does acetylcholine (ACH) get released instead of Epinephrine (EP) and Norepinephrine (NE)?

    <p>Sweat gland innervation</p> Signup and view all the answers

    What is the main neurotransmitter released from the presynaptic neuron in a typical neuron?

    <p>Acetylcholine (ACH)</p> Signup and view all the answers

    What is the function of phosphatase in smooth muscle contraction?

    <p>Removes Pi from myosin</p> Signup and view all the answers

    Study Notes

    Smooth Muscle vs. Skeletal Muscle

    • Lack striations, less myosin, no troponin (calmodulin)
    • Dense bodies instead of Z lines
    • Involuntary, responds to stretch, chemicals, temperature
    • Ca2+ from ECF, less developed SR
    • Slow, sustained contractions

    Characteristics of Smooth Muscle

    • Actin bound to dense bodies, anchored to ECF and other smooth muscles
    • Creates work through contraction
    • Located in vessels (tunica media)
    • Not directly connected to neurons, no neuromuscular junction
    • Innervated by autonomic nerves (not somatic)
    • Autonomic neurons contain varicosities (swellings with NT storage)
    • Release norepinephrine and acetylcholine

    Types of Smooth Muscle

    • Multi-unit smooth muscle:
      • Can have own autonomic nerve connection
      • Does not fire spontaneously
      • Does not contract in response to stretch
    • Single-unit smooth muscle:
      • Contains gap junctions
      • Contracts as a unit (AP propagates from cell to cell)
      • Can be spontaneously active (fluctuating threshold potential)
      • Stretch can induce contraction

    Stimulating Smooth Muscle

    • Autonomic nerves (excite or inhibit)
    • Chemicals (hormones, CO2, O2, NO, low pH, temperature, stretch)
    • Ca2+ concentration increase:
      • "Leak channel"
      • Voltage-gated channel
      • Ligand-gated channel
      • Stretch-activated channel
      • IP3 pathway
      • Calcium-induced calcium release
    • Ca2+ concentration decrease:
      • Ca ATPase out of the cell
      • Ca ATPase into the SR
      • Ca2+/Na+ countertransporter

    Smooth Muscle Contraction Pathway

    • Ca2+ enters via Ca2+ channels
    • Ca2+ binds to calmodulin to form Ca-calmodulin
    • Ca-calmodulin activates myosin light chain kinase (Ca-calmodulin MLCK) complex
    • Phosphorylates light chain on myosin head (1) and activates myosin ATPase
    • Myosin heads bind to actin and pull actin back toward its tail
    • Actin pulls on dense bodies and the cell contracts
    • ATP comes back and removes the myosin head from actin and resets the cross-bridge cycle

    Phasic Contraction and Tonic Contraction

    • Phasic contraction: similar to skeletal muscle contraction
    • Tonic contraction (latch bridge mechanism):
      • Myosin head binds to actin and waits for ATP to come in and remove myosin head
      • Phosphatase comes in and cleaves Pi, leaving myosin head bound to actin without Pi
      • ATP has lessened affinity to bind and remove myosin head, maintaining tension

    Autonomic Nervous System (ANS)

    • Visceral efferent motor
    • Innervates smooth muscle, cardiac muscle, and glands
    • Sympathetic and parasympathetic divisions
    • Sympathetic: "fight or flight" response
    • Parasympathetic: "rest and digest" response
    • Both divisions work in tandem, never fully turning off or on

    Sympathetic and Parasympathetic Innervation

    • Sympathetic:
      • Preganglionic neurons: T1-T12 and upper 2-3 segments of the spinal cord
      • Postganglionic neurons: short, unmyelinated
      • Receptors: alpha and beta adrenergic
    • Parasympathetic:
      • Preganglionic neurons: cranial nerves 3, 7, 9, and 10, and sacral portion of the spinal cord
      • Postganglionic neurons: long, unmyelinated
      • Receptors: muscarinic and nicotinic cholinergic

    Adrenergic and Cholinergic Receptors

    • Adrenergic receptors respond to norepinephrine (NE) or epinephrine (EPI)
    • Alpha and beta receptors:
      • Alpha 1: smooth muscle, visceral organs (GI tract), vasoconstriction
      • Alpha 2: presynaptic, inhibits NE release
      • Beta 1: heart, increases rate and contractility
      • Beta 2: respiratory, uterine, and GI smooth muscle, vasodilation
    • Cholinergic receptors respond to acetylcholine (ACH)
    • Muscarinic and nicotinic receptors:
      • Muscarinic: second messenger
      • Nicotinic: ligand-gated

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Physiology lecture 6.txt

    Description

    Test your knowledge on the signaling pathway involved in muscle contraction, from Ca+ entering via channels to myosin heads binding to actin. Identify the sequence of events leading to the contraction of muscle cells.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser